• 대한약리학회지
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• 제23권2호
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• pp.57-75
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• 1987

Two modalities of gonadotropin secretion, pulsatile gonadotropin and preovulatory gonadotropin surge, have been identified in the mammals. Pulsatile gonadotropin secretion is modulated by the pulsatile pattern of GnRH release and complex ovarian steroid feedback actions. The neural mechansim that regulates the pulsatile release of GnRH in the hypothalamus is called "GnRH pulse generator". Ovarian steroids, estradiol and progesterone, appear to exert thier feedback effects both directly on the pituitary to modulate gonadotropin release and on a hypothalamic site to modulate GnRH release; estradiol primarily affects the amplitude while progesterone decreases the frequency of the pulsatile GnRH. Steroid hormones are known to affect catecholamine transmission in brain. MBH-POA is richly innervated by NE systems and close apposition of NE terminals and GnRH cell bodies occurs in the MBH as well as in the POA. NE normally facilitates pulsatile LH release by acting through ${\alpha}-receptor$ mechanism. However, precise nature of facilitative role of NE transmission in maintaining pulsatile LH has not been clearly understood. Close apposition of DA and GnRH terminals in ME might permit DA to influence GnRH release. Action of DA transmission probably is mediated by axo-axonic contacts between GnRH and DA fibers in the ME. Dopamine transmission does not normally regulate pulsatile LH release, but under certain conditions, increased DA transmission inhibit LH pulse. Endogenous opioid acts to suppress the secretion of GnRH into hypophysial portal circulation, thereby inhibiting gonadotropin secretion. However, an interaction between endogenenous opioid peptides and gonadotropin release is a complex one which involves ovarian hormones as well. LH secretion appears to be most suppressed by endogenenous opioids during the luteal phase, at a time of elevated progesterone secretion. The arcuate nucleus contains not only cell bodies for GnRH and ${\beta}-endorphin$ but also a dense aborization of fibers suggesting that GnRH release is changed by the interactions between GnRH and ${\beta}-endorphin$ cell bodies within the arcuate nucleus. The frequency and amplitude of pulsatile LH release seem to be increased during the preovulatory gonadotropin surge. Estradiol exerts positive feedback action on the hypothalamo-pituitary axis to trigger preovulatory LH surge. GnRH is also crucial hormonal stimulus for preovulatory LH surge. It is unlikely, however, that increased secretion of GnRH during the preovulatory gonadotropin surge represents an obligatory neural signal for generation of the LH discharge in primates including human. Modulation of preovulatory LH surge by catecholamines has been studied almost exclusively in rats. NE and E may be involved in distinct way to accumulate GnRH in the MBH and its release into the hypophysial portal system during the critical period for LH surge on proestrus in rats. However, the mechanisms whereby augmented adrenergic transmission may facilitate the formation and accumulation of GnRH in the ME-ARC nerve terminals before the LH surge have not been clearly understood.

• 한국안전학회지
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• 제33권2호
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• pp.32-38
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• 2018

The sprinkler system is a basic fire extinguishing system widely used, but there is a lack of quantitative assessment of its performance. In this study, to evaluate the fire extinguishing performance of the sprinkler head according to the discharge coefficients, experiments were conducted. Experimental sprinkler heads were selected with heads having K50, K80 and K115 water discharge coefficients, and the fire source was assumed to be an indoor fire in Class A Model 1. As experimental results, the time required for the fire chamber to cool down to $200^{\circ}C$ was 26 seconds for the K115 head, 414 seconds for the K80 head, and 481 seconds for the K50 head, so the cooling time of the K115 head was decreased by 94.5% compared to K50 head. In the case of restoring the oxygen concentration to 15%, the K115 head did not decrease below the oxygen concentration of 15%, and the K80 head took 145 seconds and the K50 head took 484 seconds. The lowest oxygen concentration in the fire chamber was 16.1% for the K115 head, 14.33% for the K80 head, and 11.28% for the K50 head, indicating that the K115 head was superior to the K80 and K50 heads by 13.1% and 43.7%, respectively. As the experimental results show, there is big difference in the extinguishing performance depending on the discharge coefficients of the sprinkler head. Therefore, in designing the sprinkler system, the discharge coefficients of the sprinkler head should be selected considering the heat release rate at the installation site and the fire extinguishing characteristics of sprinkler head.

• 오토저널
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• 제10권4호
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• pp.66-74
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• 1988

The ignition quality of ignition system is influenced by spark energy, discharge pattern of spark energy and spark duration. In this paper, the characteristics of multiple spark ignition system have been investigated for various number of spark and spark interval. The results, which were compared with those obtained with a standard single spark ignition, show that engine output is increased, and lean misfire limit is extended with the multiple spark ignition system. The most effective number of spark at the most effective spark interval that are determined by engine performance test, were 6 times spark at 0.02ms spark interval. For the above condition of spark, engine torque was increased about 20% comparing with conventional ignition system and lean misfire limit was extended to air-fuel ratio 22.5:1. This study researched the rate of heat release and quantity of heat release influenced by a condition of spark on the mass burned in order to investigate the relationship between the rate of mass burned and number of spark times.

• 한국물환경학회지
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• 제26권5호
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• pp.789-795
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• 2010

Suspended Solid (SS) is one of the main pollutants and discharges with attached other pollutants such as heavy metal and toxic substance. It is very important to estimate and forecast the release characteristics of SS for water quality improvement. The current studies assumed that SS release rate is proportional to the rain intensity and suggested exponential washoff models. These models related to the shear force of flow. In this study, a new washoff model is suggested based on relation with SS release rate and mean flow rate of the basin surface which is closely related to the shear force. The proposed model is applied to the Goonja drainage district in Seoul, Korea. The new washoff model simulates the SS discharge more accurately in the various rainfall types. The model can be widely applied to the real problems such as the management of non-point source pollutant and the design of treatment facilities.

• 한국생산제조학회지
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• 제25권1호
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• pp.54-61
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• 2016

Washing machine manufacturers typically advise consumers to maintain the relative humidity in the drum less than 80% for three days after the termination of a washing cycle in order to prevent bacteria proliferation. A vent installed in the back of a washing machine is used to release moisture to satisfy this condition. Up to now, the design and installation of the vent have been based on experiments without understanding its roles and physical phenomena. In this study, various CFD results are presented in order to explain the physical mechanism of moisture release in a washing machine. Two methods of moisture release (diffusion and convection) were studied; diffusion was found to be the dominant process in removing moisture. Experiments were also performed to validate this behavior. In addition, this study will aid in the efficient design of vents to keep the relative humidity low inside the drum.

• Animal Bioscience
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• 제36권9호
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• pp.1376-1383
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• 2023

Objective: We aimed to determine the effects of 12-oxoeicosatetraenoic acid (12-KETE)-induced placenta release on the performance of mother cows (milk yield, ovarian function, and blood plasma biochemical properties). Methods: Experimental treatments were as follows: i) natural delivery including natural placental release (control cows); ii) induced calf delivery with placental retention (RP cows); and iii) induced calf delivery and 12-KETE-induced placental release (KE cows). Delivery in pregnant KE cows was induced with dexamethasone and prostaglandin. These cows were injected with 12-KETE after calf discharge, resulting in the release of the fetal placenta. RP cows were not treated with 12-KETE after inducing delivery, resulting in placental retention. Results: The milk yield in RP cows during the first 50 days after delivery was significantly lower than that in control cows (p<0.05), whereas KE cows exhibited a similar milk yield to that of control cows. The postpartum plasma progesterone levels of control cows increased 14 days after delivery on average; however, its increase was delayed by 10 days in RP cows. Meanwhile, the 12-KETE treatment (KE cows) brought the timing of progesterone increase forward to the normal level (control cows). Among the 20 biochemical parameters examined, the total cholesterol levels in blood plasma 14 days after delivery were lower in RP cows than that in the other two treatment groups (control cows and KE cows) (p<0.05). In addition, the plasma level of haptoglobin tended to be low in cows that discharged their placentas shortly after delivery. Conclusion: These findings indicate that 12-KETE treatment can alleviate the disorder caused by placental retention.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2002년도 추계학술발표회
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• pp.21-23
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• 2002

Two sampling methods for chlorofluorocarbons(CFCs) in groundwater were compared and assessed with groundwater samples in Jeju Island. CFCs concentrations from copper tube method were widely variable among triplicates and higher than those from flame-sealed glass ampule method. For the copper tube method, this is aggravated by rubber packings in the faucet of discharge line of wells, which was removed for the glass ampule method. The poor reproducibility and apparent contamination of results by copper tube method is due to the improper sealing of copper tubes and materials in water discharge line. This suggests that it is more difficult to achieve complete isolation from the atmosphere in the copper tube method and that materials that could release CFCs should be avoided along the sampling flow lines. It seems that the flame-sealed glass ampule method is more relevant for groundwater sampling for CFCs though it requires more complicated equipments and procedures.

• 한국유체기계학회 논문집
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• 제12권2호
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• pp.46-51
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• 2009

Recently, microturbines have received attention as a small-scale distributed power generator. Since the exhaust gas carries all of the heat release, generating hot water is usual method of heat recovery from microturbine CHP (combined heat and power) systems. The power of microturbines decreases as ambient temperature increases. This study predicted micoturbine power boost by injecting hot water generated by heat recovery. Influence of injecting water at two different locations was examined. Water injection improves power, but efficiency depends much on the injection location. Injecting water at the compressor discharge shows a much higher efficiency than the combustor injection. However, the combustor injection may have as much available cogeneration heat as the dry operation, while the available heat in the compressor discharge injection is much smaller than the dry operation.

• Annals of Occupational and Environmental Medicine
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• 제35권
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• pp.34.1-34.8
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• 2023

Background: Hydrogen sulfide is a toxic substance that humans can be exposed to occupationally, and cases of hydrogen sulfide poisoning of workers in industrial sites are commonly reported. However, there have been no cases of poisoning of the public due to an unauthorized discharge of wastewater, so it is important to describe this incident. Case presentation: In a small village in Jeollanam-do, Republic of Korea, accounts of a terrible stench had been reported. A 26-year-old man who lived and worked in a foul-smelling area was taken to the emergency room with a headache, dizziness, nausea, and repeated syncope. A subsequent police and Ministry of Environment investigation determined that the cause of the stench was the unauthorized discharge of 9 tons of wastewater containing hydrogen sulfide through a stormwater pipe while the villagers were sleeping. The patient had no previous medical history or experience of symptoms. Leukocytes and cardiac markers were elevated, an electrocardiogram indicated biatrial enlargement, left ventricular hypertrophy, and corrected QT interval prolongation. Myocardial hypertrophy was detected on a chest computed tomography scan, and hypertrophic cardiomyopathy was confirmed on echocardiography. After hospitalization, cardiac marker concentrations declined, symptoms improved, and the patient was discharged after 7 days of hospitalization. There was no recurrence of symptoms after discharge. Conclusions: We suspect that previously unrecognized heart disease manifested or was aggravated in this patient due to exposure to hydrogen sulfide. Attention should be paid to the possibility of unauthorized discharge of hydrogen sulfide, etc., in occasional local incidents and damage to public health. In the event of such an accident, it is necessary to have government guidelines in place to investigate health impact and follow-up clinical management of exposed residents.

• 한국수자원학회논문집
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• 제46권12호
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• pp.1169-1180
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• 2013

본 연구에서는 복하천 중상류 유역에 대해 준분포형 유역수문모형 SWAT-K를 적용하여 자연유량을 산정하고, 하천유량 변화를 야기하는 지하수 양수량, 하천수 취수량, 하수처리수 방류량 등의 인위적인 요인으로 인한 영향을 평가하였다. 2006년부터 2013년까지의 자연상태의 하천유량을 모의한 결과 최저유량은 $1.7m^3/s$, 평균유량은 $26.2m^3/s$, 갈수량은 약 $2.0m^3/s$로 산정되었다. 지하수 이용, 하천수 취수, 하수처리수 방류 등 각각의 인위적 요인에 의한 하천유황의 상대적 변화를 분석한 결과, 갈수량은 지하수 양수로 인해 자연상태에 비해 약 34% 감소, 하수처리수 방류와 하천수 취수의 복합 영향으로 인해 약 15% 증가, 지하수 양수, 하수처리수 방류와 하천수 취수의 복합 영향으로 약 19% 만큼 감소하는 것으로 분석되었다. 복하천 본류를 따라 모의된 자연유량 자료를 이용하여 비유량의 거동 특성을 분석한 결과, 중상류 유역에서는 지배면적이 증가할수록 비풍수량, 비평수량, 비저수량, 비갈수량 등의 값이 증가하는 경향을 나타내었으며, 하류부로 내려오면서 지배면적이 약 180 $km^2$ 이상에서부터는 면적과 상관없이 거의 일정한 비유량 값을 나타내는 것으로 분석되었다.